A composite camshaft has a shaft and separately fabricated constituent members, such as gears, cams, sprockets and journals fixedly mounted on the shaft. The shaft-end constituent member and the shaft is joined with each other with the intervention of a joint pin located in the boundary between the shaft and the constituent member. For example, the camshaft disclosed by Pat. No. U 58-37901 has the sprocket wheel fixed to the shaft by a pin passing through a bore in the boundary between the shaft and the sprocket wheel. However, the constituent member and the shaft generally differ in material so that the boundary portion is not easily drilled. Therefore, the drilled bore is not accurate but sometimes eccentric or disorderly in dimension. The problem becomes more serious when the composite camshaft has a steel shaft and cam lobes and journals made of a sintered alloy material. The reason for this is that the sintered alloy elements, such as chromium and copper, diffuse toward the shaft to form a hard cementation layer and make the boundary too hard to be machined.
The present invention is intended to resolve the problem as described above and provide a shaft member in which the fitting portions between the camshaft and the shaft-end constituent member are so formed that no joint bore is drilled in the boundary therebetween.